"... what remained to be done, was to qualify the noun 'energy' by appropriate adjectives, so as to distinguish between energy of activity and energy of configuration. The well-known pair of antithetical adjectives, 'actual' and 'potential,' seemed exactly suited for that purpose. ... Sir William Thomson and Professor Tait have lately substituted the word 'kinetic' for 'actual.'" William John Macquorn Rankine (1867). "On the Phrase "Potential Energy," and on the Definitions of Physical Quantities". Proceedings of the Philosophical Society of Glasgow. VI (III).
Fitzpatrick, Richard (20 July 2010). "Fine Structure of Hydrogen". Quantum Mechanics. Archived from the original on 25 August 2016. Retrieved 20 August 2016.
Fitzpatrick, Richard (20 July 2010). "Fine Structure of Hydrogen". Quantum Mechanics. Archived from the original on 25 August 2016. Retrieved 20 August 2016.